This proposal outlines a direct biochemical approach to an evaluation of the possible relationship between membrane transport of anticancer agents and responsiveness of human cancer. Methodology involves studies of drug transport in isolated plasma membrane vesicles. This system offers these advantages over studies in whole cells: (1) Since the contents of the cell are eliminated, it permits measurements of transport uncomplicated by intracellular metabolism or macromolecular binding characteristic of many anticancer agents, (2) it permits a meaningful analysis of membrane transport phenomena in solid tumors, which otherwise is not possible, and (3) it allows a repetitive study of transport in clinical material under stable biochemical conditions. Preparation of vesicles will be monitored by electron microscopy and analyzed for purity by determination of enzyme markers specific for organelle membranes. Verification of specific transport parameters in vesicles versus intact cell preparations will first be sought in model murine tumors. Technology developed will be applied to similar studies of selected human tumors. The information derived can be exploited for new analog development by a direct analysis of structure-activity relationships in animal and human tumors at the level of membrane transport and for the biochemical prediction of therapeutic response in human tumors prior to therapy. The relevance of drug transport to the development of acquired resistance in patients following relapse can also be evaluated by this approach.